1. Field of the Invention
The present invention relates to a method and apparatus for cleaning underwater pylons, and, more particularly, for removing marine growth, such as mussels, from pylons which support offshore platforms and the like.
2. Description of the Prior Art
Underwater pylons, which support structures such as offshore oil platforms, must be inspected periodically to insure that the integrity of the structure is still intact. Marine growth, such as mussels etc., continually accumulates on underwater structures from the surface of the water to about sixty feet below the surface. Such marine growth may extend out from the surface of the structure to twelve or more inches and must be removed prior to each inspection so that any deterioration of the pylons can be ascertained and repairs made or sections replaced.
In the past, divers have directed high velocity water streams against the pylons to remove the marine growth therefrom. The high velocity streams are issued from nozzles which deliver up to twenty gallons of water per minute at pressure up to sixty thousand pounds per square inch ("p.s.i."). The hoses and nozzles from which the high velocity streams issue are difficult for the divers to maneuver around the pylons. Furthermore, the high velocity streams are dangerous and require considerable skill on the part of the divers. As a result of the time and skill required to clean marine growth off of the pylons with the prior art apparatus the resulting cost is high.
Various devices have been devised in the prior art for cleaning underwater surfaces such as the hulls of ships, swimming pools etc. For example, U.S. Pat. No. 3,251,331 to W. R. Crawford discloses a hull cleaner in which a vacuum is created at the mouth of a wheeled carriage to cause water to flow between the mouth and the hull surface. The carriage is designed to be wheeled along the surface of the ship's hull so that the flow of water across the hull surface will dislodge the barnacles etc. The Crawford cleaner is designed to clean light marine growth, such as barnacles and algae, off of relatively smooth flat surfaces that are located near the water surface. The flat surface is necessary in order to enable carriage to create the necessary vacuum. Such a device would not be useful in removing a heavy accumulation of marine growth from relatively small diameter pylons.
U.S. Pat. Nos. 3,258,801 3,073,727 and 3,734,853 disclose devices for removing the debris from the bottom of swimming pools and aquariums. Such devices, however, would be of no use removing marine growth from underwater pylons. U.S. Pat. No. 2,204,584 to H. B. Flower discloses an apparatus for dredging the ocean floor to harvest shell fish therefrom. As in the Crawford device, this apparatus utilizes a vacuum cleaner type nozzle, which is designed to be moved across a relatively flat surface. The nozzle is designed to be rolled across the ocean floor by the dredging vessel. The vacuum cleaner type nozzles of Crawford and Flower could not be maneuvered around small diameter surfaces (e.g. 24 inches or less in diameter) such as the exterior surfaces of pylons and would not create sufficient vacuum on such a curved surface to dislodge the marine growth.
The disadvantages of the prior art techniques and apparatus for cleaning underwater pylons which support offshore platforms have been overcome by the present invention.